Help me calculate floor space in my loft

jas72

jas72

jas72

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I'm thinking of getting my loft converted and have to raise the pitch of my roof from 30° to 40°

MY house is detached and is 8m X 15m of useable loft space but of course I won't have it all. I was looking for a calulation as I'm sure it's quite simple to do but I can't work it out
 
Do you mean the pitch of the roof will make some areas unusable?

Surely that is up to the individual about how tolerant they are to low ceilings (ie are you a midget?)
 
If the usable floor space is what you've said, why should the pitch of the roof matter?

Explain things properly, because I have no idea what the problem is!
 
Well the height in the center of the roof will change if I change the (pitch) angle of the roof, legal floorspace is calculated at 2.3m in height so whilst technically i'll have 8X15m floor space i'd like to know what floor space i'd have where the height will be 2.3m or more.

I've found a site that shows with a 40% pitch my height at center will be 3.35m

now to calculate how much headspace that gives either side.
 
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J.B said:
Do you mean the pitch of the roof will make some areas unusable?

Surely that is up to the individual about how tolerant they are to low ceilings (ie are you a midget?)
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That's probably waht he means. I'd stick furniture in the low areas but yeah, it's really what you find comfortable.

Not sure if the Building Regs have any requirements on minimum ceiling heights.

Calcs will be simple geometry and trigonometry.
 
jas72 said:
I'm thinking of getting my loft converted and have to raise the pitch of my roof from 30° to 40°

MY house is detached and is 8m X 15m of useable loft space but of course I won't have it all. I was looking for a calulation as I'm sure it's quite simple to do but I can't work it out
Click to expand...

Correct me if am wrong.... You are converting you roof space but have to replace the whole roof and you don't know how much usable space you are going to end up with or have to start with? If you are having the roof removed why not just keep the old roof and build the brick work up 4 foot and then put the roof back on.
 
At 2.3m minimum headheight you will lose 2.7m either end off the 18m.

It's easier to think in terms of what space you lose in the corners. Using a website like http://ostermiller.org/calc/triangle.html put in the 40 degree angle, 90 dgree angle and vertical height required, and it will tell you how much you lose each end.

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Orcish-Horde said:
Correct me if am wrong.... You are converting you roof space but have to replace the whole roof and you don't know how much usable space you are going to end up with or have to start with? If you are having the roof removed why not just keep the old roof and build the brick work up 4 foot and then put the roof back on.
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It's a possiblity as well of course but the roof is now 30 years old and it's trussed I probably couldn't keep it without loosing my ceilings below.

But yeah there are some minimums for lofts The steeper the pitch the headroom I get.
 
Abyss said:
At 2.3m minimum headheight you will lose 2.7m either end off the 18m.

It's easier to think in terms of what space you lose in the corners. Using a website like http://ostermiller.org/calc/triangle.html put in the 40 degree angle, 90 dgree angle and vertical height required, and it will tell you how much you lose each end.

32313973.gif
Click to expand...

thanks but the roof sits the other way and is 8m wide.
 
jas72 said:
thanks but the roof sits the other way and is 8m wide.
Click to expand...

Exactly the same but take the numbers off 8m instead of 15m. So you will have 2.6m.

I would suggest considering 1.2m as "usable space" (i.e. where you put your stud walls with storage space behind), and 2m as "usable headroom".


1.2m gives a room size of 18m x 5.2m
2m gives a headheight area of 18m x 3.2m
 
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jas72 said:
It's a possiblity as well of course but the roof is now 30 years old and it's trussed I probably couldn't keep it without loosing my ceilings below.

But yeah there are some minimums for lofts The steeper the pitch the headroom I get.
Click to expand...

Sound like you will need to re enforce the flooring up there as well. Imo if your taking the roof of, build up the brick work you will get much more benifit.
 
Depending on how much you want to use upstairs and how manuch stuff you want to add, it woudl be worthwhile having a better survey of the loft done - floor joist capacity, timber quality etc.

I'm sure there are DIY forums about but some pics/sketches would help and I can have a look at the joist capacities if you know how big they are, what centres and how long.

Sketchup might be a good easy software to try modelling your loft to get an idea of what it will look like or toy with layouts.
 
thanks for the replies guys.

I've tried working it out using calculator tools and I clearly would benefit from raising the pitch of my roof.

I'm looking to add 2 large bedrooms and a bathroom upstairs.

Great idea about the 1.2 as useable

If I take the right angled triangle and use

30° as my pitch my height at center is 2.3m this gives me around about 2m wide at 1.7m height which is clearly useless in terms of having a liveable space.

However by changing the pitch to 40°then the height at center is 3.36m which gives me around about 4m at 1.7m height and 5.2m at 1.2m giving me 15X5.2m useable floorspace
 
have you looked into the building regs? making your loft a habitable space isn't as straight forward as it seems. you will need to take the fire regulations into account and build to these or building control wil make you alter it - can be very expensive if you get it wrong.
 
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